On the Dumbledore subject, I think that Dumbledore's aggression isn't down to the actor, it's down to the person who wrote those scenes. Michael Gambon doesn't have any control over how they want him to portray Dumbledore. I think he's doing brilliantly. I prefer him happy or wise though, not angry. I think that he feels he is like Dumbledore, so doesn't bother to work on the calm side.
However, Harris was the perfect Dumbledore. He spoke in the way I imagined Dumbledore to speak, he was calm and wise, just as JKR discribed in the book. RIP Richard Harris.